Hi Madison,
I think your concept to build a post war style layout had merit. First, being on a budget, you have lots of items to choose from that can be used on your layout at relatively good prices. For example, Lionel tubular track is plentiful, and there are ways to remove rust, etc, to make them useable. Switches can be rebuilt/reconditioned, you can use manual switches in place of automatic, especially in locations near the edge of your layout. Get a Greenberg Manual to learn how to do repairs (get a used one on amazon).
A 6x10 is a large layout, I would make it is several sections that you can take apart and store, if needed. Lumber is expensive, if there is a custom door store near where you live, they may have used doors available cheap. They are very sturdy and relatively light (hollow core) so you could get four doors and use mending plates or door hindges (they may have some used ones) to attach them together. For the base, saw horses are a good start, however, if you have a construction company that does home remodels,you can see if they have any used kitchen cabinents from work sites. They may also have scrap lumber available. The point is to spend as little as possible on materials.
For track plans, some of us really like the Lionel display layouts that they used to build for department stores. You might be able to find a copy of Lionel Display Layouts You can Build at your local library. Its out of print and somewhat expensive. CTT has run articles on display layouts over the years, and Jim Barrett built an updated version of the D-265 in OGR a while back.
i would say that most of us are natural bargin hunters and hate to throw anything away, so re-purposing scrap stuff to use on your layout is a worthy goal. Fixing old engines and rail cars, is rewarding and there are lots of people on the forum that can help you.
Here is a picture of a manual switched that I rebuilt with one that had not been worked on.
Good luck and keep us posted.
